To realize a stream multiplexer performing stream multiplexing and PCR correction with a simple configuration.

An input time measuring part 12 measures the input time of each packet included in an input stream. An input controlling part 13 writes each packet data and the input time included in the input stream into buffer memory 18. An output order deciding means 16 decides the output order of the packets written in the memory 18. A PCR correcting means 17 rewrites a PCR by using the input time and an output time stored in the buffer memory 11 when the PCR is included in the packet whose output order is decided by the means 16. An output controlling part 14 reads and outputs packet data from the memory 18 in the order decided by the means 11.